package com.baeldung.stepverifier; import org.junit.Test; import reactor.core.publisher.Flux; import reactor.test.StepVerifier; import java.time.Duration; public class PostExecutionUnitTest { Flux source = Flux.create(emitter -> { emitter.next(1); emitter.next(2); emitter.next(3); emitter.complete(); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } emitter.next(4); }).filter(number -> number % 2 == 0); @Test public void droppedElements() { StepVerifier.create(source) .expectNext(2) .expectComplete() .verifyThenAssertThat() .hasDropped(4) .tookLessThan(Duration.ofMillis(1500)); } }